I'm using a Dell Dimension 4550 to run various Linux OSes, mostly from
the 80GB internal HDD.
However, I want more!!
But, being a Dell computer, there is no option available to boot from
an external (usb) HDD so I have being using this guide (https://
help.ubuntu.com/community/BootFromUSB) which explains how to modify
the initrd file and subsequently reconfigure the kernel module to
allow booting from a usb HDD even when the computer BIOS does not
recognise the drive.
The guide is written for Ubuntu and it works great for this OS as well
as for Ubuntustudio. I have also managed to use it to boot to
SimplyMEPIS on a usb drive.
However, I'm currently having problems adapting this method to boot
PCLinuxOS from an external drive.
There appear to be two reasons for this:

1) the files to be modified to allow booting from the usb drive are
not available in PCLinuxOS. These are
/etc/mkinitramfs/modules (or /etc/initramfs-tools/modules in newer
Ubuntu) and /etc/mkinitramfs/initramfs.conf (or /etc/initramfs-tools/
initramfs.conf in newer Ubuntu).
I would like to know what are the equivalent files in PCLinuxOS.

2) Having made the required modifications, the next step is to rebuild
the initrd files. This is done using dpkg-reconfigure linux-image-
<kernelversion>.
However, PCLinux doesn't seem to use the dpkg-reconfigure command as
it's not contained in /usr/sbin/ and typing this in a terminal/konsole
in PCLinuxOS gives a "command not found" error.
Once again, my question is, what is the equivalent command in
PCLinuxOS for this procedure?

What is strange is that I was able to get PCLinuxOS to boot from a usb
HDD on this same computer about a year ago. But, for the life of me, I
just can't figure out what I did. In any event, it does show that what
I'm trying to do is absolutely possible if only I wasn't so
forgettful.

I'll be grateful for any advice.
Thanks
Paul